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JMS was often used just for asynchronous execution of synchronous methods. Now you can achieve the same with a single annotation: @Asynchronous. The following EJB 3.1 stores a JPA entity in an asynchronous way:

@Path("message")

@Stateless

public class MessagingService {

    @PersistenceContext

    EntityManager em;

    @POST

    @Asynchronous

    public void newMessage(String content){

        em.persist(new Message(content));

    }

    @Asynchronous

    public Future<Long> create(String content){

        Message message = new Message(content);

        em.persist(message);

        em.flush();

        em.refresh(message);

        return new AsyncResult<Long>(message.getId());

    }

} 

The method newMessage will be executed asynchronously, but still transactional, in the application servers thread pool.  The method create returns Future, and can return so a result. It will either be executed in background thread or synchronous - if you invoke it too early. So it doesn't fit exactly to the Fire And Forget paradigm.

A deployable, working example (project Fire And Forget) was tested with Glassfish v3b70 and NetBeans 6.8beta and pushed into http://kenai.com/projects/javaee-patterns/.  Btw. the whole WAR file (EJB 3.1 + REST) takes 8kB on the hard drive....

[See Lightweight Asynchronous Facade pattern, page 65 in "Real World Java EE Patterns Rethinking Best Practices" book for more in-depth discussion] 

Posted at 11:51AM Nov 10, 2009 by Adam Bien in Real World Java EE Patterns - Rethinking Best Practices  |  Kommentare[0]

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